//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//  Rendering main loop and setup functions,
//   utility functions (BSP, geometry, trigonometry).
//  See tables.c, too.
//





#include <stdlib.h>
#include <math.h>


#include "doomdef.h"
#include "d_loop.h"

#include "m_bbox.h"
#include "m_menu.h"

#include "r_local.h"
#include "r_sky.h"





// Fineangles in the SCREENWIDTH wide window.
#define FIELDOFVIEW     2048



int         viewangleoffset;

// increment every time a check is made
int         validcount = 1;


lighttable_t*       fixedcolormap;
extern lighttable_t**   walllights;

int         centerx;
int         centery;

fixed_t         centerxfrac;
fixed_t         centeryfrac;
fixed_t         projection;

// just for profiling purposes
int         framecount;

int         sscount;
int         linecount;
int         loopcount;

fixed_t         viewx;
fixed_t         viewy;
fixed_t         viewz;

angle_t         viewangle;

fixed_t         viewcos;
fixed_t         viewsin;

player_t*       viewplayer;

// 0 = high, 1 = low
int         detailshift;

//
// precalculated math tables
//
angle_t         clipangle;

// The viewangletox[viewangle + FINEANGLES/4] lookup
// maps the visible view angles to screen X coordinates,
// flattening the arc to a flat projection plane.
// There will be many angles mapped to the same X.
int         viewangletox[FINEANGLES/2];

// The xtoviewangleangle[] table maps a screen pixel
// to the lowest viewangle that maps back to x ranges
// from clipangle to -clipangle.
angle_t         xtoviewangle[SCREENWIDTH+1];

lighttable_t*       scalelight[LIGHTLEVELS][MAXLIGHTSCALE];
lighttable_t*       scalelightfixed[MAXLIGHTSCALE];
lighttable_t*       zlight[LIGHTLEVELS][MAXLIGHTZ];

// bumped light from gun blasts
int         extralight;



void (*colfunc) (void);
void (*basecolfunc) (void);
void (*fuzzcolfunc) (void);
void (*transcolfunc) (void);
void (*spanfunc) (void);



//
// R_AddPointToBox
// Expand a given bbox
// so that it encloses a given point.
//
void
R_AddPointToBox
( int       x,
  int       y,
  fixed_t*  box )
{
    if (x< box[BOXLEFT])
    box[BOXLEFT] = x;
    if (x> box[BOXRIGHT])
    box[BOXRIGHT] = x;
    if (y< box[BOXBOTTOM])
    box[BOXBOTTOM] = y;
    if (y> box[BOXTOP])
    box[BOXTOP] = y;
}


//
// R_PointOnSide
// Traverse BSP (sub) tree,
//  check point against partition plane.
// Returns side 0 (front) or 1 (back).
//
int
R_PointOnSide
( fixed_t   x,
  fixed_t   y,
  node_t*   node )
{
    fixed_t dx;
    fixed_t dy;
    fixed_t left;
    fixed_t right;

    if (!node->dx)
    {
    if (x <= node->x)
        return node->dy > 0;

    return node->dy < 0;
    }
    if (!node->dy)
    {
    if (y <= node->y)
        return node->dx < 0;

    return node->dx > 0;
    }

    dx = (x - node->x);
    dy = (y - node->y);

    // Try to quickly decide by looking at sign bits.
    if ( (node->dy ^ node->dx ^ dx ^ dy)&0x80000000 )
    {
    if  ( (node->dy ^ dx) & 0x80000000 )
    {
        // (left is negative)
        return 1;
    }
    return 0;
    }

    left = FixedMul ( node->dy>>FRACBITS , dx );
    right = FixedMul ( dy , node->dx>>FRACBITS );

    if (right < left)
    {
    // front side
    return 0;
    }
    // back side
    return 1;
}


int
R_PointOnSegSide
( fixed_t   x,
  fixed_t   y,
  seg_t*    line )
{
    fixed_t lx;
    fixed_t ly;
    fixed_t ldx;
    fixed_t ldy;
    fixed_t dx;
    fixed_t dy;
    fixed_t left;
    fixed_t right;

    lx = line->v1->x;
    ly = line->v1->y;

    ldx = line->v2->x - lx;
    ldy = line->v2->y - ly;

    if (!ldx)
    {
    if (x <= lx)
        return ldy > 0;

    return ldy < 0;
    }
    if (!ldy)
    {
    if (y <= ly)
        return ldx < 0;

    return ldx > 0;
    }

    dx = (x - lx);
    dy = (y - ly);

    // Try to quickly decide by looking at sign bits.
    if ( (ldy ^ ldx ^ dx ^ dy)&0x80000000 )
    {
    if  ( (ldy ^ dx) & 0x80000000 )
    {
        // (left is negative)
        return 1;
    }
    return 0;
    }

    left = FixedMul ( ldy>>FRACBITS , dx );
    right = FixedMul ( dy , ldx>>FRACBITS );

    if (right < left)
    {
    // front side
    return 0;
    }
    // back side
    return 1;
}


//
// R_PointToAngle
// To get a global angle from cartesian coordinates,
//  the coordinates are flipped until they are in
//  the first octant of the coordinate system, then
//  the y (<=x) is scaled and divided by x to get a
//  tangent (slope) value which is looked up in the
//  tantoangle[] table.

//




angle_t
R_PointToAngle
( fixed_t   x,
  fixed_t   y )
{
    x -= viewx;
    y -= viewy;

    if ( (!x) && (!y) )
    return 0;

    if (x>= 0)
    {
    // x >=0
    if (y>= 0)
    {
        // y>= 0

        if (x>y)
        {
        // octant 0
        return tantoangle[ SlopeDiv(y,x)];
        }
        else
        {
        // octant 1
        return ANG90-1-tantoangle[ SlopeDiv(x,y)];
        }
    }
    else
    {
        // y<0
        y = -y;

        if (x>y)
        {
        // octant 8
        return -tantoangle[SlopeDiv(y,x)];
        }
        else
        {
        // octant 7
        return ANG270+tantoangle[ SlopeDiv(x,y)];
        }
    }
    }
    else
    {
    // x<0
    x = -x;

    if (y>= 0)
    {
        // y>= 0
        if (x>y)
        {
        // octant 3
        return ANG180-1-tantoangle[ SlopeDiv(y,x)];
        }
        else
        {
        // octant 2
        return ANG90+ tantoangle[ SlopeDiv(x,y)];
        }
    }
    else
    {
        // y<0
        y = -y;

        if (x>y)
        {
        // octant 4
        return ANG180+tantoangle[ SlopeDiv(y,x)];
        }
        else
        {
         // octant 5
        return ANG270-1-tantoangle[ SlopeDiv(x,y)];
        }
    }
    }
    return 0;
}


angle_t
R_PointToAngle2
( fixed_t   x1,
  fixed_t   y1,
  fixed_t   x2,
  fixed_t   y2 )
{
    viewx = x1;
    viewy = y1;

    return R_PointToAngle (x2, y2);
}


fixed_t
R_PointToDist
( fixed_t   x,
  fixed_t   y )
{
    int     angle;
    fixed_t dx;
    fixed_t dy;
    fixed_t temp;
    fixed_t dist;
    fixed_t     frac;

    dx = abs(x - viewx);
    dy = abs(y - viewy);

    if (dy>dx)
    {
    temp = dx;
    dx = dy;
    dy = temp;
    }

    // Fix crashes in udm1.wad

    if (dx != 0)
    {
        frac = FixedDiv(dy, dx);
    }
    else
    {
    frac = 0;
    }

    angle = (tantoangle[frac>>DBITS]+ANG90) >> ANGLETOFINESHIFT;

    // use as cosine
    dist = FixedDiv (dx, finesine[angle] );

    return dist;
}




//
// R_InitPointToAngle
//
void R_InitPointToAngle (void)
{
    // UNUSED - now getting from tables.c
#if 0
    int i;
    long    t;
    float   f;
//
// slope (tangent) to angle lookup
//
    for (i=0 ; i<=SLOPERANGE ; i++)
    {
    f = atan( (float)i/SLOPERANGE )/(3.141592657*2);
    t = 0xffffffff*f;
    tantoangle[i] = t;
    }
#endif
}


//
// R_ScaleFromGlobalAngle
// Returns the texture mapping scale
//  for the current line (horizontal span)
//  at the given angle.
// rw_distance must be calculated first.
//
fixed_t R_ScaleFromGlobalAngle (angle_t visangle)
{
    fixed_t     scale;
    angle_t     anglea;
    angle_t     angleb;
    int         sinea;
    int         sineb;
    fixed_t     num;
    int         den;

    // UNUSED
#if 0
{
    fixed_t     dist;
    fixed_t     z;
    fixed_t     sinv;
    fixed_t     cosv;

    sinv = finesine[(visangle-rw_normalangle)>>ANGLETOFINESHIFT];
    dist = FixedDiv (rw_distance, sinv);
    cosv = finecosine[(viewangle-visangle)>>ANGLETOFINESHIFT];
    z = abs(FixedMul (dist, cosv));
    scale = FixedDiv(projection, z);
    return scale;
}
#endif

    anglea = ANG90 + (visangle-viewangle);
    angleb = ANG90 + (visangle-rw_normalangle);

    // both sines are allways positive
    sinea = finesine[anglea>>ANGLETOFINESHIFT];
    sineb = finesine[angleb>>ANGLETOFINESHIFT];
    num = FixedMul(projection,sineb)<<detailshift;
    den = FixedMul(rw_distance,sinea);

    if (den > num>>16)
    {
    scale = FixedDiv (num, den);

    if (scale > 64*FRACUNIT)
        scale = 64*FRACUNIT;
    else if (scale < 256)
        scale = 256;
    }
    else
    scale = 64*FRACUNIT;

    return scale;
}



//
// R_InitTables
//
void R_InitTables (void)
{
    // UNUSED: now getting from tables.c
#if 0
    int     i;
    float   a;
    float   fv;
    int     t;

    // viewangle tangent table
    for (i=0 ; i<FINEANGLES/2 ; i++)
    {
    a = (i-FINEANGLES/4+0.5)*PI*2/FINEANGLES;
    fv = FRACUNIT*tan (a);
    t = fv;
    finetangent[i] = t;
    }

    // finesine table
    for (i=0 ; i<5*FINEANGLES/4 ; i++)
    {
    // OPTIMIZE: mirror...
    a = (i+0.5)*PI*2/FINEANGLES;
    t = FRACUNIT*sin (a);
    finesine[i] = t;
    }
#endif

}



//
// R_InitTextureMapping
//
void R_InitTextureMapping (void)
{
    int         i;
    int         x;
    int         t;
    fixed_t     focallength;

    // Use tangent table to generate viewangletox:
    //  viewangletox will give the next greatest x
    //  after the view angle.
    //
    // Calc focallength
    //  so FIELDOFVIEW angles covers SCREENWIDTH.
    focallength = FixedDiv (centerxfrac,
                finetangent[FINEANGLES/4+FIELDOFVIEW/2] );

    for (i=0 ; i<FINEANGLES/2 ; i++)
    {
    if (finetangent[i] > FRACUNIT*2)
        t = -1;
    else if (finetangent[i] < -FRACUNIT*2)
        t = viewwidth+1;
    else
    {
        t = FixedMul (finetangent[i], focallength);
        t = (centerxfrac - t+FRACUNIT-1)>>FRACBITS;

        if (t < -1)
        t = -1;
        else if (t>viewwidth+1)
        t = viewwidth+1;
    }
    viewangletox[i] = t;
    }

    // Scan viewangletox[] to generate xtoviewangle[]:
    //  xtoviewangle will give the smallest view angle
    //  that maps to x.
    for (x=0;x<=viewwidth;x++)
    {
    i = 0;
    while (viewangletox[i]>x)
        i++;
    xtoviewangle[x] = (i<<ANGLETOFINESHIFT)-ANG90;
    }

    // Take out the fencepost cases from viewangletox.
    for (i=0 ; i<FINEANGLES/2 ; i++)
    {
    t = FixedMul (finetangent[i], focallength);
    t = centerx - t;

    if (viewangletox[i] == -1)
        viewangletox[i] = 0;
    else if (viewangletox[i] == viewwidth+1)
        viewangletox[i]  = viewwidth;
    }

    clipangle = xtoviewangle[0];
}



//
// R_InitLightTables
// Only inits the zlight table,
//  because the scalelight table changes with view size.
//
#define DISTMAP     2

void R_InitLightTables (void)
{
    int     i;
    int     j;
    int     level;
    int     startmap;
    int     scale;

    // Calculate the light levels to use
    //  for each level / distance combination.
    for (i=0 ; i< LIGHTLEVELS ; i++)
    {
    startmap = ((LIGHTLEVELS-1-i)*2)*NUMCOLORMAPS/LIGHTLEVELS;
    for (j=0 ; j<MAXLIGHTZ ; j++)
    {
        scale = FixedDiv ((SCREENWIDTH/2*FRACUNIT), (j+1)<<LIGHTZSHIFT);
        scale >>= LIGHTSCALESHIFT;
        level = startmap - scale/DISTMAP;

        if (level < 0)
        level = 0;

        if (level >= NUMCOLORMAPS)
        level = NUMCOLORMAPS-1;

        zlight[i][j] = colormaps + level*256;
    }
    }
}



//
// R_SetViewSize
// Do not really change anything here,
//  because it might be in the middle of a refresh.
// The change will take effect next refresh.
//
boolean     setsizeneeded;
int     setblocks;
int     setdetail;


void
R_SetViewSize
( int       blocks,
  int       detail )
{
    setsizeneeded = true;
    setblocks = blocks;
    setdetail = detail;
}


//
// R_ExecuteSetViewSize
//
void R_ExecuteSetViewSize (void)
{
    fixed_t cosadj;
    fixed_t dy;
    int     i;
    int     j;
    int     level;
    int     startmap;

    setsizeneeded = false;

    if (setblocks == 11)
    {
    scaledviewwidth = SCREENWIDTH;
    viewheight = SCREENHEIGHT;
    }
    else
    {
    scaledviewwidth = setblocks*32;
    viewheight = (setblocks*168/10)&~7;
    }

    detailshift = setdetail;
    viewwidth = scaledviewwidth>>detailshift;

    centery = viewheight/2;
    centerx = viewwidth/2;
    centerxfrac = centerx<<FRACBITS;
    centeryfrac = centery<<FRACBITS;
    projection = centerxfrac;

    if (!detailshift)
    {
    colfunc = basecolfunc = R_DrawColumn;
    fuzzcolfunc = R_DrawFuzzColumn;
    transcolfunc = R_DrawTranslatedColumn;
    spanfunc = R_DrawSpan;
    }
    else
    {
    colfunc = basecolfunc = R_DrawColumnLow;
    fuzzcolfunc = R_DrawFuzzColumnLow;
    transcolfunc = R_DrawTranslatedColumnLow;
    spanfunc = R_DrawSpanLow;
    }

    R_InitBuffer (scaledviewwidth, viewheight);

    R_InitTextureMapping ();

    // psprite scales
    pspritescale = FRACUNIT*viewwidth/SCREENWIDTH;
    pspriteiscale = FRACUNIT*SCREENWIDTH/viewwidth;

    // thing clipping
    for (i=0 ; i<viewwidth ; i++)
    screenheightarray[i] = viewheight;

    // planes
    for (i=0 ; i<viewheight ; i++)
    {
    dy = ((i-viewheight/2)<<FRACBITS)+FRACUNIT/2;
    dy = abs(dy);
    yslope[i] = FixedDiv ( (viewwidth<<detailshift)/2*FRACUNIT, dy);
    }

    for (i=0 ; i<viewwidth ; i++)
    {
    cosadj = abs(finecosine[xtoviewangle[i]>>ANGLETOFINESHIFT]);
    distscale[i] = FixedDiv (FRACUNIT,cosadj);
    }

    // Calculate the light levels to use
    //  for each level / scale combination.
    for (i=0 ; i< LIGHTLEVELS ; i++)
    {
    startmap = ((LIGHTLEVELS-1-i)*2)*NUMCOLORMAPS/LIGHTLEVELS;
    for (j=0 ; j<MAXLIGHTSCALE ; j++)
    {
        level = startmap - j*SCREENWIDTH/(viewwidth<<detailshift)/DISTMAP;

        if (level < 0)
        level = 0;

        if (level >= NUMCOLORMAPS)
        level = NUMCOLORMAPS-1;

        scalelight[i][j] = colormaps + level*256;
    }
    }
}



//
// R_Init
//



void R_Init (void)
{
    R_InitData ();
    printf (".");
    R_InitPointToAngle ();
    printf (".");
    R_InitTables ();
    // viewwidth / viewheight / detailLevel are set by the defaults
    printf (".");

    R_SetViewSize (screenblocks, detailLevel);
    R_InitPlanes ();
    printf (".");
    R_InitLightTables ();
    printf (".");
    R_InitSkyMap ();
    R_InitTranslationTables ();
    printf (".");

    framecount = 0;
}


//
// R_PointInSubsector
//
subsector_t*
R_PointInSubsector
( fixed_t   x,
  fixed_t   y )
{
    node_t* node;
    int     side;
    int     nodenum;

    // single subsector is a special case
    if (!numnodes)
    return subsectors;

    nodenum = numnodes-1;

    while (! (nodenum & NF_SUBSECTOR) )
    {
    node = &nodes[nodenum];
    side = R_PointOnSide (x, y, node);
    nodenum = node->children[side];
    }

    return &subsectors[nodenum & ~NF_SUBSECTOR];
}



//
// R_SetupFrame
//
void R_SetupFrame (player_t* player)
{
    int     i;

    viewplayer = player;
    viewx = player->mo->x;
    viewy = player->mo->y;
    viewangle = player->mo->angle + viewangleoffset;
    extralight = player->extralight;

    viewz = player->viewz;

    viewsin = finesine[viewangle>>ANGLETOFINESHIFT];
    viewcos = finecosine[viewangle>>ANGLETOFINESHIFT];

    sscount = 0;

    if (player->fixedcolormap)
    {
    fixedcolormap =
        colormaps
        + player->fixedcolormap*256*sizeof(lighttable_t);

    walllights = scalelightfixed;

    for (i=0 ; i<MAXLIGHTSCALE ; i++)
        scalelightfixed[i] = fixedcolormap;
    }
    else
    fixedcolormap = 0;

    framecount++;
    validcount++;
}



//
// R_RenderView
//
void R_RenderPlayerView (player_t* player)
{
    R_SetupFrame (player);

    // Clear buffers.
    R_ClearClipSegs ();
    R_ClearDrawSegs ();
    R_ClearPlanes ();
    R_ClearSprites ();

    // check for new console commands.
    NetUpdate ();

    // The head node is the last node output.
    R_RenderBSPNode (numnodes-1);

    // Check for new console commands.
    NetUpdate ();

    R_DrawPlanes ();

    // Check for new console commands.
    NetUpdate ();

    R_DrawMasked ();

    // Check for new console commands.
    NetUpdate ();
}
